Problem in calculating vortex using Q criterion

Amber0922 · July 2, 2023, 23:33

Hi, everyone
I am currently conducting calculations for the backward facing step and intend to plot the vortex using Q criterion. I have set the mean velocity in x, y, and z directions under 'Analyze - Field Variable' and selected 'Q criterion' under 'Calculate Variables'. Subsequently, I have set the Iso-Surface as Q with a value of 300.
However, my results appear anomalous as they depict a ring-like structure instead of conforming to expected outcomes. Could you please advise if there are any errors in my operations? Thank you for your assistance.

sjsivabharathy · August 24, 2023, 02:32

Hi Amber,

I think the value of Q you have set is too high.
Did you try for lower values? Please give more details about the
solver you used for computing the flow and the Reynolds number.

Also did you look at the streamlines and vorticity field?

Please refer to my work where the flow structures are identified
via Q criterion using Tecplot.

1) https://www.cambridge.org/core/journ...9B75CD#article
2) https://www.cambridge.org/core/journ...3385E1#metrics
3) https://pubs.aip.org/aip/pof/article...tion-bubble-in

Regards,
Jawahar.

July 2, 2023, 23:33	Problem in calculating vortex using Q criterion	#1
Amber0922 Member Zhang Join Date: Mar 2023 Posts: 72 Rep Power: 3	Hi, everyone I am currently conducting calculations for the backward facing step and intend to plot the vortex using Q criterion. I have set the mean velocity in x, y, and z directions under 'Analyze - Field Variable' and selected 'Q criterion' under 'Calculate Variables'. Subsequently, I have set the Iso-Surface as Q with a value of 300. However, my results appear anomalous as they depict a ring-like structure instead of conforming to expected outcomes. Could you please advise if there are any errors in my operations? Thank you for your assistance.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Problem in calculating additional variable with second time derivative	ziyixy	CFX	1	April 24, 2021 23:01
getting problem in calculating torque required for centrifugal pump	sarfarazii	Main CFD Forum	1	September 9, 2015 05:59
Problem of calculating divergence due to wrong boundary vaule of finite area mesh	lzhou	OpenFOAM Programming & Development	2	June 18, 2015 06:10
[ICEM] low edge criterion value problem	mraxx	ANSYS Meshing & Geometry	6	April 30, 2013 10:03
Problem: calculating drag coefficient	RFH_student	FLUENT	3	February 8, 2011 09:36

August 24, 2023, 02:32		#2
sjsivabharathy New Member jawahar sivabharathy Join Date: Jan 2011 Posts: 12 Rep Power: 15	Hi Amber, I think the value of Q you have set is too high. Did you try for lower values? Please give more details about the solver you used for computing the flow and the Reynolds number. Also did you look at the streamlines and vorticity field? Please refer to my work where the flow structures are identified via Q criterion using Tecplot. 1) https://www.cambridge.org/core/journ...9B75CD#article 2) https://www.cambridge.org/core/journ...3385E1#metrics 3) https://pubs.aip.org/aip/pof/article...tion-bubble-in Regards, Jawahar.